(1) Field of the Invention
The present invention relates to materials for use in electronic devices, in particular in organic electroluminescent devices.
(2) Description of Related Art
The structure of organic electroluminescent devices (OLEDs) in which organic semiconductors are employed as functional materials is described, for example, in U.S. Pat. Nos. 4,539,507, 5,151,629, EP 0676461 and WO 98/27136. The emitting materials employed here are increasingly organometallic complexes which exhibit phosphorescence instead of fluorescence (M. A. Baldo et al., Appl. Phys. Lett. 1999, 75, 4-6). For quantum-mechanical reasons, an up to four-fold increase in energy and power efficiency is possible using organometallic compounds as phosphorescence emitters. In general, however, there is still a need for improvement, for example with respect to efficiency, operating voltage and in particular lifetime, in OLEDs, in particular also in OLEDs which exhibit triplet emission (phosphorescence). This applies, in particular, to OLEDs which emit in the relatively short-wavelength range, for example green.
The properties of phosphorescent OLEDs are determined not only by the triplet emitters employed. In particular, the other materials used, such as matrix materials, hole-blocking materials, electron-transport materials, hole-transport materials and electron- or exciton-blocking materials, are also of particular importance here. Improvements in these materials can thus also result in significant improvements in the OLED properties. There is also still a need for improvement in these materials for fluorescent OLEDs.
In accordance with the prior art, ketones (for example in accordance with WO 04/093207 or WO 10/006680) or phosphine oxides (for example in accordance with WO 05/003253), inter alia, are used as matrix materials for phosphorescent emitters. However, there is still a need for improvement, in particular with respect to the efficiency and lifetime of the device, on use of these matrix materials as in the case of other matrix materials. The object of the present invention is the provision of compounds which are suitable for use in a fluorescent or phosphorescent OLED, in particular a phosphorescent OLED, for example as matrix material or as hole-transport/electron-blocking material or exciton-blocking material or as electron-transport or hole-blocking material. In particular, the object of the present invention is to provide matrix materials which are suitable for green- and red-phosphorescent OLEDs.
Surprisingly, it has been found that certain compounds described in greater detail below achieve this object and result in significant improvements in the organic electroluminescent device, in particular with respect to the lifetime, efficiency and operating voltage. This applies, in particular, to red- and green-phosphorescent electroluminescent devices, especially on use of the compounds according to the invention as matrix material. The present invention therefore relates to these materials and to organic electroluminescent devices which comprise compounds of this type.
WO 07/031165 discloses bridged triarylamine structures having a similar basic structure to the compounds according to the invention. However, compounds which are substituted by the substituents according to the invention mentioned below are not disclosed therein. Furthermore, these compounds are only described as emitters or hole-transport materials, but not as matrix materials for phosphorescent emitters or as electron-transport materials.
US 2009/0136779 discloses compounds having a similar basic structure as matrix for phosphorescent emitters. However, compounds which are substituted by the substituents according to the invention mentioned below are not disclosed therein.